左外连接的 Linq 查询无法正常工作

Question

我将 sql 查询转换为 linq 查询，没有任何错误。

现在，我的问题是我在 sql 查询中正确获取数据，而在 linq 查询中显示整个数据而不过滤 product null.

这是我的代码：

SQL查询

SELECT Name
FROM ProductMaster product
LEFT JOIN TouchWastageGroup touchWastageGroup ON touchWastageGroup.Product = product.Name and touchWastageGroup.GroupNameId = 2 and touchWastageGroup.CaratId = 6
WHERE touchWastageGroup.Product IS NULL

从这个查询数据显示正常。

Linq 查询

var productSelected = (from product in _productMasterRepository.Table
from touchWastageGroup in _touchWastageGroupRepository.Table
.Where(touchWastageGroup => touchWastageGroup.Product == product.Name && touchWastageGroup.GroupNameId == 2 && touchWastageGroup.CaratId == 6)                                   
.DefaultIfEmpty().Where(x => x.Product == null)
select new
{
   Result = product.Name
}).ToList();

linq 的相同查询显示整个数据而不过滤此 (Where(x => x.Product == null)).

是不是linq语法或查询有问题？

Answer 1

尝试使用这个查询

var productSelected = from product in _productMasterRepository.Table
join from touchWastageGroup in _touchWastageGroupRepository.Table on
product.Name equals touchWastageGroup.Product into temp
from t in temp.DefaultIfEmpty()
where t.GroupNameId == 2 && t.CaratId == 6
select new
{
   Result = product.Name
}).ToList();

Answer 2

检查以下查询 return 没有产品

from product in _productMasterRepository.Table
join touchWastageGroup in _touchWastageGroupRepository.Table on new { Product = product.Product, GroupNameId = 2, CaratId = 6 } equals new { touchWastageGroup.Product, touchWastageGroup.GroupNameId, touchWastageGroup.CaratId } into joinedResult
from touchWastageGroup in joinedResult.DefaultIfEmpty()
where touchWastageGroup == null
select new { Result = product.Name }

左外连接的 Linq 查询无法正常工作

Linq query of left outer join not properly working

c#

sql

linq

filtering

sql-to-linq-conversion